JP2017196745A - Printing device and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem due to charging of a recording medium.SOLUTION: A printing device includes: a drive roller which drives a recording medium in a prescribed direction by rotating; a support member which supports the recording medium at a downstream side in the prescribed direction with respect to the drive roller; a discharge head which is provided so as to face the support member and discharges liquid to the recording medium supported by the support member; a tension control unit which adjusts tension of the recording medium supported by the support member by controlling the tension of the recording medium on the basis of a result obtained by detecting the tension of the recording medium at the downstream side in the prescribed direction with respect to the drive roller; and a first static elimination unit which eliminates static electricity of the recording medium at the upstream side in the prescribed direction with respect to the drive roller.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for eliminating charge from a recording medium used for printing.

  A printing apparatus (printer) described in Patent Document 1 includes a recording head arranged to face a rotating drum, and discharges ink from the recording head while supporting the recording medium (sheet) with the rotating drum. Print an image on However, such a printing apparatus may cause various problems due to charging of the recording medium.

JP 2014-184665 A

  As an example, there is a case where an influence on the tension control of the recording medium occurs. That is, in Patent Document 1, the driving roller is provided on the upstream side in the recording medium conveyance direction from the support member (rotating drum) that supports the recording medium. Further, the tension of the recording medium supported by the support member is controlled by controlling the tension of the recording medium based on the result of detecting the tension of the recording medium on the downstream side in the transport direction from the driving roller. Accordingly, it is possible to appropriately control the tension of the recording medium on which the liquid ejected from the ejection head is landed. However, if the recording medium is charged, the recording medium sticks to the driving roller when passing through the driving roller. In some cases, the sticking of the recording medium to the driving roller affects the detection result of the tension of the recording medium, so that the tension control of the recording medium cannot be performed properly (first problem).

  Alternatively, as another example, there is a case where the contamination of the ejection head is affected. That is, when the recording medium is charged, the liquid in the form of mist tends to adhere to the surface of the ejection head facing the recording medium. In addition, there has been a situation in which such mist-like liquid adhesion to the ejection head cannot be easily eliminated by charge removal of the recording medium.

  That is, it is conceivable to use a static eliminator such as an ionizer for static elimination of the recording medium. In addition, as such a static eliminator, there is known a static eliminator that eliminates static electricity with ions generated by applying an alternating voltage to a plurality of arranged electrodes. However, since there is a tendency that a large amount of ions are given to the portion of the recording medium facing the electrode, uneven discharge due to the arrangement of the electrodes occurs, and the discharge head has a mist shape at a location corresponding to the uneven discharge. In some cases, the liquid adheres (second problem).

  In addition, since the ion balance is inappropriate, the recording medium supported by the support member cannot be sufficiently neutralized, and mist-like liquid may adhere to the ejection head that faces the support member (third case). Task).

  The present invention has been made in view of the above, and an object thereof is to provide a technique for solving at least one of the above-described problems.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects.

  A first aspect (printing apparatus) of the present invention is a driving roller that drives a recording medium in a predetermined direction by rotating, a supporting member that supports the recording medium downstream of the driving roller in a predetermined direction, and opposed to the supporting member. A discharge head that discharges the liquid to the recording medium that is provided and supported by the support member, and the tension of the recording medium is controlled based on the result of detecting the tension of the recording medium downstream of the driving roller in a predetermined direction. A tension control unit that adjusts the tension of the recording medium supported by the support member, and a first neutralization unit that neutralizes the recording medium upstream of the driving roller in a predetermined direction.

  The second aspect (printing method) of the present invention includes a step of driving the recording medium in a predetermined direction by the driving roller by rotating the driving roller, and discharging the recording medium by the neutralizing unit upstream of the driving roller in the predetermined direction. A step of adjusting the tension of the recording medium supported by the support member by controlling the tension of the recording medium based on the result of detecting the tension of the recording medium on the downstream side in the predetermined direction from the driving roller; And a step of discharging a liquid from a discharge head facing the support member to a recording medium supported by a support member provided on the downstream side in a predetermined direction.

  In the present invention (the first aspect and the second aspect) configured as described above, the recording medium is neutralized by the neutralizing unit on the upstream side in the predetermined direction with respect to the driving roller that drives the recording medium in the predetermined direction. Therefore, since the recording medium has been neutralized when passing through the driving roller, sticking of the recording medium to the driving roller is suppressed. As a result, the tension of the recording medium can be accurately detected on the downstream side in the predetermined direction from the drive roller, and the tension control of the recording medium can be appropriately performed.

  In addition, the printing apparatus may be configured to include a discharger that performs a surface modification process on the recording medium by applying discharge energy to the recording medium upstream in the predetermined direction from the first static elimination unit. In other words, in a printing apparatus equipped with a discharger, the amount of charge of the recording medium tends to increase, so that the influence on tension control due to the charged recording medium sticking to the drive roller also increases. On the other hand, the recording medium tension can be appropriately controlled by neutralizing the recording medium by the neutralizing unit upstream of the driving roller in the predetermined direction.

  In addition, the printing apparatus may be configured to include a second neutralization unit that neutralizes the recording medium between the driving roller and the ejection head. In this way, the recording medium is neutralized in two stages before reaching the ejection head, so that the recording medium is completely neutralized, and mist-like liquid adheres to the ejection head due to the charging of the recording medium. Can be suppressed.

  At this time, the printing apparatus may be configured such that the second static elimination unit is provided to face the support member. Accordingly, the recording medium can be neutralized in the vicinity of the ejection head, and the mist-like liquid can be prevented from adhering to the ejection head due to charging of the recording medium.

  Moreover, you may comprise a printing apparatus so that the surface of a supporting member may be coat | covered with the insulating layer. That is, when the surface of the support member has conductivity, ions generated in the static elimination section face a portion of the support member that is not hidden by the recording medium, and there is a possibility that the ions cannot be firmly applied to the recording medium. On the other hand, by covering the surface of the support member with the insulating layer, the ions generated in the charge eliminating portion can be firmly applied to the recording medium, and the recording medium can be more reliably discharged.

  In addition, the first static elimination unit and the second static elimination unit neutralize the recording medium by applying ions generated by applying an alternating voltage to the plurality of arranged electrodes to the recording medium. The printing apparatus may be configured such that the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the second static elimination unit is smaller than the amplitude of the AC voltage generated in the recording medium by the applied AC voltage. .

  In such a configuration, a first static elimination unit arranged on the upstream side and a second static elimination unit arranged on the downstream side are provided in a predetermined direction in which the recording medium is conveyed. Further, an AC voltage having a relatively large amplitude is generated on the recording medium due to the AC voltage applied to the electrode of the first static elimination unit. For this reason, there is a large difference in the amount of ions applied between the portion to which ions are densely applied and the portion to which ions are loosely applied, and the charge removal unevenness is likely to occur in the recording medium that has been neutralized by the first static elimination portion. . On the other hand, the second static elimination unit further neutralizes the recording medium after the static elimination by the first static elimination unit. In addition, the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the second static elimination unit is relatively small. Therefore, compared with the first static elimination unit, the second static elimination unit can uniformly eliminate the recording medium, and it is possible to alleviate the static elimination unevenness of the recording medium after the static elimination by the first static elimination unit. . As a result, it is possible to suppress the mist-like liquid from adhering to the ejection head.

  At this time, the first static elimination unit has a plurality of electrodes provided on one side of the recording medium and a plurality of electrodes provided on the other side of the recording medium. The printing apparatus may be configured so that the phase of the alternating voltage applied is different from the phase of the alternating voltage applied to the plurality of electrodes on the other surface side by 180 degrees. Alternatively, the printing apparatus may be configured such that the distance between the electrode of the first charge eliminating unit and the recording medium is narrower than the distance between the electrode of the second charge eliminating unit and the recording medium. In these printing apparatuses, an AC voltage having a relatively large amplitude is generated on the recording medium due to the AC voltage applied to the electrode of the first static elimination unit. Therefore, by providing the second static elimination unit as described above, it is preferable to alleviate the static elimination unevenness of the recording medium after the static elimination by the first static elimination unit.

  Further, the printing apparatus may be configured so that the pitch at which the plurality of electrodes are arranged at the first static elimination unit and the pitch at which the plurality of electrodes are arranged at the second static elimination unit are different. In this way, by making the pitch at which the electrodes are arranged different between the first static elimination unit and the second static elimination unit, the neutralization unevenness of the recording medium after the static elimination by the first static elimination unit is effectively reduced by the second static elimination unit. Can do.

  In addition, the printing apparatus may be configured to include an adjustment unit that adjusts the ion balance of the first static elimination unit and a potential detector that detects the potential of the recording medium supported by the support member. In such a configuration, the ion balance of the static elimination unit can be adjusted while confirming the detection result of the potential of the recording medium supported by the support member. Therefore, it is possible to optimize the ion balance. As a result, it is possible to suppress the mist-like liquid from adhering to the ejection head.

  At this time, the printing apparatus is configured to include a balance control unit that controls the ion balance of the first static elimination unit by causing the adjustment unit to adjust the ion balance of the first static elimination unit based on the detection result of the potential detector. Also good. In such a configuration, the ion balance can be automatically optimized by the balance control unit.

  Or you may comprise a printing apparatus so that the display part which shows the detection result of an electric potential detector, and the balance control part which adjusts the ion balance of a 1st static elimination part according to input operation may be provided. In such a configuration, the user can perform an input operation while confirming the detection result of the potential detector displayed on the display unit, so that the ion balance can be optimized.

  According to a third aspect (printing apparatus) of the present invention, there is provided a transport unit that transports a recording medium in a predetermined direction, a support member that supports the recording medium, and a recording medium that is provided to face the support member and is supported by the support member. A discharge head that discharges liquid to the discharge head, and an ion generated by applying an AC voltage to a plurality of electrodes arranged in an upstream side in a predetermined direction from the discharge head, thereby removing the charge from the recording medium. The first charge eliminating unit, and between the first charge eliminating unit and the ejection head, the recording medium is neutralized by applying ions generated by applying an alternating voltage to the plurality of arranged electrodes to the recording medium. And an AC voltage generated on the recording medium by the AC voltage applied to the electrode of the second static elimination unit based on the amplitude of the AC voltage generated on the recording medium by the AC voltage applied to the electrode of the first static elimination unit. Small voltage amplitude It is characterized in.

  A fourth aspect (printing apparatus) of the present invention includes a step of conveying a recording medium in a predetermined direction, and a step of discharging liquid from a discharge head provided opposite to the support member to a recording medium supported by the support member. Discharging the recording medium by applying to the recording medium ions generated by applying an alternating voltage to a plurality of electrodes arranged in a first discharging section provided upstream of the ejection head in a predetermined direction; A step of discharging the recording medium by applying to the recording medium ions generated by applying an alternating voltage to a plurality of electrodes arranged in a second discharging section provided between the first discharging section and the discharge head; And the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the second charge eliminating unit is smaller than the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the first discharging unit. Features .

  In the present invention thus configured (third aspect, fourth aspect), in the predetermined direction in which the recording medium is conveyed, the first static elimination part arranged on the upstream side and the second static elimination part arranged on the downstream side And are provided. Further, an AC voltage having a relatively large amplitude is generated on the recording medium due to the AC voltage applied to the electrode of the first static elimination unit. For this reason, there is a large difference in the amount of ions applied between the portion to which ions are densely applied and the portion to which ions are loosely applied, and the charge removal unevenness is likely to occur in the recording medium that has been neutralized by the first static elimination portion. . On the other hand, the second static elimination unit further neutralizes the recording medium after the static elimination by the first static elimination unit. In addition, the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the second static elimination unit is relatively small. Therefore, compared with the first static elimination unit, the second static elimination unit can uniformly eliminate the recording medium, and it is possible to alleviate the static elimination unevenness of the recording medium after the static elimination by the first static elimination unit. . As a result, it is possible to suppress the mist-like liquid from adhering to the ejection head.

  According to a fifth aspect (printing apparatus) of the present invention, there is provided a conveyance unit that conveys a recording medium in a predetermined direction, a support member that supports the recording medium, and a recording medium that is provided opposite to the support member and supported by the support member. A discharge head that discharges liquid to the discharge head, and a discharge that is provided upstream of the discharge head in a predetermined direction and discharges the recording medium by applying ions generated by applying an alternating voltage to the arranged electrodes to the recording medium. And an adjustment unit that adjusts the ion balance of the charge removal unit, and a potential detector that detects the potential of the recording medium supported by the support member.

  A sixth aspect (printing method) of the present invention includes a step of conveying a recording medium in a predetermined direction, and a step of discharging liquid from a discharge head provided facing the support member to a recording medium supported by the support member. A step of discharging the recording medium by applying to the recording medium ions generated by applying an AC voltage to an electrode arranged in a discharging section provided upstream of the discharge head in a predetermined direction, and a support member supporting the discharge medium And a step of adjusting the ion balance of the charge removal unit based on the detected potential.

  In the present invention (the fifth aspect and the sixth aspect) configured as described above, the ion balance of the static eliminating unit can be adjusted while confirming the detection result of the potential of the recording medium supported by the support member. Therefore, it is possible to optimize the ion balance. As a result, it is possible to suppress the mist-like liquid from adhering to the ejection head.

  Note that not all of the plurality of constituent elements included in each aspect of the present invention described above are essential, and in order to solve part or all of the above-described problems or a part of the effects described in the present specification. Or, in order to achieve all of them, it is possible to change, delete, replace with other new components, or delete some of the limited contents of some components of the plurality of components as appropriate. is there. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

FIG. 3 is a diagram illustrating an internal configuration of a printer to which the invention is applied. The figure which shows the structure of a 1st static elimination part. The figure which shows the structure of a 2nd static elimination part. The figure which shows the electrical constitution which controls a printer. The figure which shows the structure which performs the 1st control example of the static elimination process of a sheet | seat. The figure which shows the time change of the voltage which a 1st and 2nd static elimination part produces in a sheet | seat. The figure which shows the structure which performs the 2nd control example of the static elimination process of a sheet | seat.

  FIG. 1 is a front view schematically showing an example of the internal configuration of a printer to which the present invention is applied. As shown in FIG. 1, in the printer 1, one sheet S (web) whose both ends are wound around the feeding shaft 20 and the winding shaft 40 in a roll shape is interposed between the feeding shaft 20 and the winding shaft 40. The sheet S is stretched, and the sheet S is transported from the feeding shaft 20 to the winding shaft 40 along the transport path Pc thus stretched. In other words, both ends of the sheet S are wound in a roll shape to form a feeding roll R20 and a winding roll R40. The feeding roll R20 supported on the feeding shaft 20 is pivotally supported on the winding shaft 40. The sheet S is conveyed by a roll-to-roll along the conveyance direction Ds toward the taken-up roll R40.

  In the printer 1, an image is recorded on the sheet S conveyed in the conveyance direction Ds. The type of the sheet S is roughly classified into a paper type and a film type. Specific examples include high-quality paper, cast paper, art paper, coated paper, and the like for paper, and synthetic paper, PET (Polyethylene terephthalate), PP (polypropylene), and the like for film. Schematically, the printer 1 includes a feeding unit 2 (feeding region) that feeds the sheet S from the feeding shaft 20, a process unit 3 (process region) that records an image on the sheet S fed from the feeding unit 2, and a process. A winding unit 4 (winding region) for winding the sheet S on which the image is recorded in the unit 3 around the winding shaft 40 is provided. In the following description, among the both surfaces of the sheet S, the surface facing the recording head 51 is referred to as the front surface, and the opposite surface is referred to as the back surface.

  The feeding unit 2 includes a feeding shaft 20 around which the end of the sheet S is wound, and a driven roller 21 around which the sheet S drawn from the feeding shaft 20 is wound. The feeding shaft 20 supports the end of the sheet S by winding the end thereof with the surface of the sheet S facing outward. Then, when the feeding shaft 20 rotates clockwise in FIG. 1, the sheet S wound around the feeding shaft 20 is fed to the process unit 3 via the driven roller 21. Incidentally, the sheet S is wound around the feeding shaft 20 via a core tube 22 that can be attached to and detached from the feeding shaft 20. Therefore, when the sheet S of the feeding shaft 20 is used up, it is possible to replace the sheet S of the feeding shaft 20 by attaching a new core tube 22 around which the roll-shaped sheet S is wound to the feeding shaft 20. It has become.

  In the feeding unit 2, the corona treatment device 7 is disposed between the feeding shaft 20 and the driven roller 21 in the conveyance direction Ds of the sheet S. The corona treatment device 7 includes a support roller 71 that winds the sheet S from the feeding shaft 20 to the driven roller 21 from the back surface side, and a corona discharger 73 that faces the surface of the support roller 71 via the sheet S. The support roller 71 is grounded and functions as a ground electrode. On the other hand, the corona discharger 73 includes a corona discharge electrode 731 and an electrode cover 733 that covers the corona discharge electrode 731. The corona discharge electrode 731 is disposed so as to face the support roller 71 with the sheet S interposed therebetween, and generates corona discharge between the support roller 71 when a voltage is applied. In this way, corona discharge energy is applied to the surface of the sheet S wound around the support roller 71, so that the surface of the sheet S is subjected to corona treatment (surface modification treatment).

  Further, the feeding unit 2 includes a first static elimination unit 81 provided on the downstream side in the transport direction Ds from the driven roller 21. The first charge removal unit 81 includes a front surface ionizer 82 that faces the front surface of the sheet S and a back surface ionizer 83 that faces the rear surface of the sheet S, and the sheet S is discharged by the ionizers 82 and 83. In this way, the feeding unit 2 feeds the sheet S, which has been subjected to the surface modification treatment by the corona treatment device 7 and then has been neutralized by the first static elimination unit 81, to the process unit 3.

  The process unit 3 supports the sheet S fed from the feeding unit 2 by the rotary drum 30 and performs processing by the functional units 51, 52, 61, 62, and 63 arranged along the outer peripheral surface of the rotary drum 30. An image is recorded on the sheet S as appropriate. In the process unit 3, a front drive roller 31 and a rear drive roller 32 are provided on both sides of the rotary drum 30, and the sheet S conveyed from the front drive roller 31 to the rear drive roller 32 is supported by the rotary drum 30. And receive an image record.

  The front drive roller 31 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and supports the sheet S fed from the feeding unit 2 from the back side. The front drive roller 31 rotates in the clockwise direction in FIG. 1 to convey the sheet S fed out from the feeding unit 2 to the downstream side in the transport direction Ds. A nip roller 31 n is provided for the front drive roller 31. The nip roller 31n is in contact with the surface of the sheet S while being urged toward the front drive roller 31, and sandwiches the sheet S between the front drive roller 31 and the nip roller 31n. Thereby, the frictional force between the front drive roller 31 and the sheet S is ensured, and the sheet S can be reliably conveyed by the front drive roller 31.

  The rotary drum 30 is a cylindrical drum having a diameter of, for example, 400 [mm] that is rotatably supported by a support mechanism (not shown), and is conveyed from the front drive roller 31 to the rear drive roller 32. Wrap from the back side. The rotating drum 30 supports the sheet S from the back side while receiving the frictional force between the rotating sheet 30 and rotating in the conveying direction Ds of the sheet S. Incidentally, the process unit 3 is provided with driven rollers 33 and 34 for folding the sheet S on both sides of the winding part around the rotary drum 30. Among these, the driven roller 33 wraps the surface of the sheet S between the front driving roller 31 and the rotary drum 30 and folds the sheet S. On the other hand, the driven roller 34 wraps the surface of the sheet S between the rotary drum 30 and the rear drive roller 32 and folds the sheet S. In this way, by folding the sheet S on the upstream and downstream sides in the transport direction Ds with respect to the rotating drum 30, it is possible to secure a long winding portion of the sheet S around the rotating drum 30.

  The rear drive roller 32 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and supports the sheet S conveyed from the rotary drum 30 via the driven roller 34 from the back surface side. Then, the rear drive roller 32 conveys the sheet S to the winding unit 4 by rotating clockwise in FIG. A nip roller 32n is provided for the rear drive roller 32. The nip roller 32 n is in contact with the surface of the sheet S while being urged toward the rear drive roller 32, and sandwiches the sheet S between the rear drive roller 32. Accordingly, a frictional force between the rear drive roller 32 and the sheet S is ensured, and the sheet S can be reliably conveyed by the rear drive roller 32.

  Thus, the sheet S conveyed from the front drive roller 31 to the rear drive roller 32 is supported on the outer peripheral surface of the rotary drum 30. In the process unit 3, in order to record a color image on the surface of the sheet S supported by the rotary drum 30, a plurality of recording heads 51 corresponding to different colors are provided. Specifically, four recording heads 51 corresponding to yellow, cyan, magenta, and black are arranged in the transport direction Ds in this color order. Each recording head 51 is opposed to the surface of the sheet S wound around the rotary drum 30 with a slight clearance, and discharges the corresponding color ink (colored ink) from the nozzles by an ink jet method. Then, each recording head 51 ejects ink onto the sheet S conveyed in the conveyance direction Ds, whereby a color image is formed on the surface of the sheet S.

  Incidentally, as the ink, UV (ultraviolet) ink (photo-curable ink) that is cured by irradiating ultraviolet rays (light) is used. Therefore, in the process unit 3, UV irradiators 61 and 62 (light irradiating units) are provided to cure the ink and fix it on the sheet S. The ink curing is performed in two stages, temporary curing and main curing. A temporary curing UV irradiator 61 is disposed between each of the plurality of recording heads 51. That is, the UV irradiator 61 cures (temporarily cures) the ink to such an extent that the shape of the ink does not collapse by irradiating a small amount of accumulated ultraviolet light, and does not completely cure the ink. On the other hand, a UV irradiator 62 for main curing is provided downstream of the recording heads 51 in the transport direction Ds. In other words, the UV irradiator 62 completely cures (mainly cures) the ink by irradiating with a greater amount of accumulated ultraviolet light than the UV irradiator 61.

  As described above, the UV irradiator 61 disposed between each of the plurality of recording heads 51 temporarily cures the colored ink discharged onto the sheet S from the recording head 51 on the upstream side in the transport direction Ds. Therefore, the ink ejected from the one recording head 51 onto the sheet S is temporarily cured before reaching the recording head 51 adjacent to the one recording head 51 on the downstream side in the transport direction Ds. As a result, the occurrence of color mixing such as mixing of colored inks of different colors is suppressed. In a state in which the color mixture is suppressed in this way, the plurality of recording heads 51 eject colored inks of different colors to form a color image on the sheet S. Further, a UV irradiator 62 for main curing is provided downstream of the plurality of recording heads 51 in the transport direction Ds. Therefore, the color image formed by the plurality of recording heads 51 is finally cured by the UV irradiator 62 and fixed on the sheet S.

  Furthermore, a recording head 52 is provided downstream of the UV irradiator 62 in the transport direction Ds. The recording head 52 is opposed to the surface of the sheet S wound around the rotating drum 30 with a slight clearance, and discharges transparent UV ink from the nozzles onto the surface of the sheet S by an inkjet method. That is, the transparent ink is further ejected with respect to the color image formed by the recording heads 51 for four colors. The transparent ink is ejected over the entire surface of the color image, and gives the color image a texture such as a glossy feeling or a matte feeling. Further, a UV irradiator 63 is provided on the downstream side of the recording head 52 in the transport direction Ds. The UV irradiator 63 irradiates strong ultraviolet rays to completely cure (main cure) the transparent ink ejected by the recording head 52. Thereby, the transparent ink can be fixed on the surface of the sheet S.

  By the way, in the printer 1 that records an image on the sheet S by discharging ink from the recording heads 51 and 52 as described above, when the charge amount of the sheet S is large, the surface of the recording heads 51 and 52 that faces the sheet S. There is a tendency that a large amount of mist ink adheres. As described above, since the first neutralization unit 81 is provided in the feeding unit 2, charging of the sheet S is suppressed to some extent. However, in the process unit 3, a second static elimination unit 85 is provided in order to more reliably suppress the mist ink from adhering to the recording heads 51 and 52. The second static eliminating portion 85 is upstream of the most upstream recording head 51 in the transport direction Ds (in other words, between the driven roller 33 and the most upstream recording head 51 in the transport direction Ds). It has a surface ionizer 86 facing the surface. Then, the sheet S is neutralized by the surface ionizer 86. Further, in the process unit 3, a potential sensor S <b> 30 that detects the potential of the surface of the sheet S is provided in order to confirm the effect of charge removal of the sheet S. The rotary drum 30 detects the potential of the surface of the sheet S wound around the rotary drum 30 between the second static elimination unit 85 and the uppermost recording head 51 in the transport direction Ds.

  As described above, in the process unit 3, ink discharge and curing are appropriately performed on the sheet S wound around the outer peripheral portion of the rotary drum 30, and a color image coated with transparent ink is formed. At this time, the sheet S to be printed with a color image in the process unit 3 is subjected to a surface modification process in advance before reaching the opposing portion of the recording heads 51 and 52. Since a color image is formed by ejecting ink to the sheet S subjected to the surface modification treatment in this way, it is possible to form a high-quality color image. Further, the sheet S is neutralized before reaching the portion facing the recording heads 51 and 52. Therefore, since the sheet S has a large amount of charge, a color image can be formed on the sheet S while suppressing a large amount of mist-like ink from adhering to the recording heads 51 and 52. Then, the sheet S on which the color image is formed is conveyed to the winding unit 4 by the rear drive roller 32.

  The winding unit 4 includes a driven roller 41 that winds the sheet S from the back side between the winding shaft 40 and the rear drive roller 32 in addition to the winding shaft 40 around which the end of the sheet S is wound. The winding shaft 40 winds and supports the end of the sheet S with the surface of the sheet S facing outward. That is, when the winding shaft 40 rotates clockwise in FIG. 1, the sheet S conveyed from the rear drive roller 32 is wound around the winding shaft 40 via the driven roller 41. Incidentally, the sheet S is wound around the winding shaft 40 via a core tube 42 that can be attached to and detached from the winding shaft 40. Therefore, when the sheet S wound around the winding shaft 40 is full, the sheet S can be removed together with the core tube 42.

  By the way, as described above, the printer 1 includes the first static elimination unit 81 arranged in the feeding unit 2 and the second static elimination unit 85 arranged in the process unit 3. Then, the structure of these 1st and 2nd static elimination parts 81 and 85 is demonstrated. FIG. 2 is an explanatory diagram schematically showing the configuration of the first static elimination unit, and FIG. 3 is a diagram schematically showing the configuration of the second static elimination unit. In FIG. 2, the sheet S is shown in addition to the first static elimination unit 81, and in FIG. 3, the sheet S and the rotary drum 30 are shown in addition to the second static elimination unit 85. The width direction Dw shown in both figures is a direction perpendicular to the transport direction Ds and parallel to the surface of the rotating drum 30, in other words, a direction parallel to the rotating shaft of the rotating drum 30.

  As shown in FIG. 2, the first static elimination unit 81 includes a front surface ionizer 82 disposed on the front surface side of the sheet S and a rear surface ionizer 83 disposed on the rear surface side of the sheet S. In the surface ionizer 82, a plurality of discharge needles 821 facing the surface of the sheet S with an interval d82 are arranged in a line at an equal pitch P82 in parallel with the width direction Dw. Further, in the back surface ionizer 83, a plurality of discharge needles 831 facing the back surface of the sheet S with an interval d83 are arranged in a line at an equal pitch P83 parallel to the width direction Dw. Here, the interval d82 and the interval d83 are equal to each other, and the pitch P82 and the pitch P83 are equal to each other. The front surface ionizer 82 and the rear surface ionizer 83 are positioned relative to each other so that one discharge needle 821 and one discharge needle 831 face each other across the sheet S. Further, the front surface ionizer 82 and the back surface ionizer 83 with respect to the conveyance path Pc of the sheet S such that the plurality of discharge needles 821 and the plurality of discharge needles 831 are protruded on both sides in the width direction Dw from the sheet S. It is positioned.

  As shown in FIG. 3, the second static elimination unit 85 has a surface ionizer 86 disposed on the surface side of the sheet S. In the surface ionizer 86, a plurality of discharge needles 861 facing the surface of the sheet S with an interval d86 are arranged in a line at an equal pitch P86 parallel to the width direction Dw. Here, the interval d86 is wider than the intervals d82 and d83 (d86> d82 = d83), and the pitch P86 is wider than the pitch P82 and the pitch P83 (P86> P82 = P83). The surface ionizer 86 is positioned with respect to the conveyance path Pc of the sheet S so that the row of the plurality of discharge needles 861 protrudes on both sides of the sheet S in the width direction Dw. Further, the rotary drum 30 is positioned so as to protrude from the row of the plurality of discharge needles 861 and the sheet S to both sides in the width direction Dw. Incidentally, the entire surface (circumferential surface) of the rotary drum 30 is covered with a black insulating layer formed by alumite treatment. Accordingly, both sides of the surface of the rotary drum 30 that are exposed to the discharge needle 861 without being covered with the sheet S are covered with the insulating layer.

  The above is the outline of the device configuration of the printer 1. Subsequently, an electrical configuration for controlling the printer 1 will be described. FIG. 4 is a block diagram showing an electrical configuration for controlling the printer shown in FIG. The printer 1 includes a printer control unit 100 that comprehensively controls each unit of the apparatus. The printer control unit 100 is a computer constituted by a CPU (Central Processing Unit) and a memory.

  The printer 1 includes a UI (User Interface) 9. The UI 9 includes a monitor configured with a liquid crystal display or the like, and an input operation unit configured with a keyboard, a mouse, or the like. A menu screen is displayed on the UI 9 monitor in addition to the image to be printed. Accordingly, the user operates the input operation unit of the UI 9 while confirming the monitor of the UI 9 to open the print setting screen from the menu screen, and various types of printing such as the type of the print medium, the size of the print medium, and the print quality. Conditions can be set. The specific configuration of the UI 9 can be variously modified. For example, a touch panel display may be used as a monitor, and the input operation unit may be configured with the touch panel of the monitor. Then, the printer control unit 100 controls each unit of the recording head, the UV irradiator, and the sheet conveyance system in the following manner in accordance with a command from an external device or an input operation to the UI 9.

  The printer control unit 100 controls the ink ejection timing of each recording head 51 that forms a color image according to the conveyance of the sheet S. Specifically, the control of the ink ejection timing is executed based on the output (detection value) of a drum encoder E30 that is attached to the rotating shaft of the rotating drum 30 and detects the rotational position of the rotating drum 30. That is, since the rotary drum 30 is driven to rotate as the sheet S is conveyed, the conveyance position of the sheet S can be grasped by referring to the output of the drum encoder E30 that detects the rotation position of the rotary drum 30. Therefore, the printer control unit 100 generates a pts (print timing signal) signal from the output of the drum encoder E30, and controls the ink ejection timing of each recording head 51 based on this pts signal, so that each recording head 51 has the same function. The ejected ink is landed on the target position of the conveyed sheet S to form a color image.

  Similarly, the timing at which the recording head 52 discharges the transparent ink is also controlled by the printer control unit 100 based on the output of the drum encoder E30. Thereby, it is possible to accurately eject the transparent ink to the color image formed by the plurality of recording heads 51. Further, the printer controller 100 also controls the timing of turning on / off the UV irradiators 61, 62, and 63 and the amount of irradiation light.

  Further, the printer control unit 100 manages a function of controlling the conveyance of the sheet S described in detail with reference to FIG. That is, motors are connected to the feeding shaft 20, the front drive roller 31, the rear drive roller 32, and the take-up shaft 40 among members constituting the sheet conveyance system. The printer control unit 100 controls the conveyance of the sheet S by controlling the speed and torque of each motor while rotating these motors. Details of the conveyance control of the sheet S are as follows.

  The printer control unit 100 rotates the feeding motor M <b> 20 that drives the feeding shaft 20, and supplies the sheet S from the feeding shaft 20 to the front drive roller 31. At this time, the printer control unit 100 controls the torque of the feeding motor M20 to adjust the tension (feeding tension Ta) of the sheet S from the feeding shaft 20 to the front drive roller 31. That is, a tension sensor S <b> 21 for detecting the feeding tension Ta is attached to the driven roller 21 disposed between the feeding shaft 20 and the front drive roller 31. The tension sensor S21 can be constituted by a load cell that detects a force received from the sheet S, for example. The printer control unit 100 adjusts the feeding tension Ta of the sheet S by feedback controlling the torque of the feeding motor M20 based on the detection result of the tension sensor S21.

  Further, the printer control unit 100 rotates the front drive motor M31 that drives the front drive roller 31 and the rear drive motor M32 that drives the rear drive roller 32. As a result, the sheet S fed from the feeding unit 2 passes through the process unit 3. At this time, speed control is executed for the front drive motor M31, while torque control is executed for the rear drive motor M32. That is, the printer control unit 100 adjusts the rotation speed of the front drive motor M31 to be constant based on the encoder output of the front drive motor M31. As a result, the sheet S is conveyed at a constant speed by the front drive roller 31.

  On the other hand, the printer control unit 100 controls the torque of the rear drive motor M32 to adjust the tension (process tension Tb) of the sheet S from the front drive roller 31 to the rear drive roller 32. That is, the tension sensor S34 for detecting the process tension Tb is attached to the driven roller 34 disposed between the rotary drum 30 and the rear drive roller 32. The tension sensor S34 can be configured by a load cell that detects a force received from the sheet S, for example. The printer control unit 100 adjusts the process tension Tb of the sheet S by feedback controlling the torque of the rear drive motor M32 based on the detection result of the tension sensor S34.

  Further, the printer control unit 100 rotates the winding motor M <b> 40 that drives the winding shaft 40, and winds the sheet S conveyed by the rear driving roller 32 around the winding shaft 40. At this time, the printer control unit 100 controls the torque of the winding motor M40 to adjust the tension (winding tension Tc) of the sheet S from the rear drive roller 32 to the winding shaft 40. That is, a tension sensor S41 for detecting the winding tension Tc is attached to the driven roller 41 disposed between the rear drive roller 32 and the winding shaft 40. The tension sensor S41 can be configured by a load cell that detects a force received from the sheet S, for example. The printer control unit 100 adjusts the winding tension Tc of the sheet S by feedback controlling the torque of the winding motor M40 based on the detection result of the tension sensor S41.

  The printer control unit 100 also has a function of controlling the corona processor 7. Specifically, the printer control unit 100 adjusts the voltage supplied to the corona discharge electrode 731 included in the corona discharger 73. Thereby, the energy used for the corona treatment can be adjusted, and the wettability of the ink with respect to the sheet S can be optimized.

  Furthermore, the printer control unit 100 controls the first static elimination unit 81 and the second static elimination unit 85 to optimize the static elimination process on the sheet S. In particular, in the first control example of the following static elimination process, the printer control unit 100 controls the first static elimination unit 81 and the second static elimination unit 85 based on the result of the drum encoder E30 detecting the surface potential of the sheet S.

  FIG. 5 is a block diagram illustrating a configuration for executing a first control example of the sheet neutralization process. As shown in the figure, the printer control unit 100 includes a power supply unit 110 that supplies a voltage to each discharge needle 821 included in the surface ionizer 82 of the first charge removal unit 81 and each of the back surface ionizers 83 included in the first charge removal unit 81. The power supply unit 120 supplies a voltage to the discharge needle 831, and the power supply unit 130 supplies the voltage to each discharge needle 861 included in the surface ionizer 86 of the second static elimination unit 85.

  The power supply unit 110 includes a DC power supply 111, an AC power supply 112, and an amplifier 113 that adds the output of the AC power supply 112 to the output of the DC power supply 111, and the output voltage of the amplifier 113 is a discharge needle of the first static elimination unit 81. 821. As a result, the output voltage of the DC power supply 111 is applied to the discharge needle 821 as a bias voltage, and the AC voltage output from the AC power supply 112 is applied around the bias voltage. As a result, the discharge needle 821 periodically and periodically discharges positive ions and negative ions in response to the supply of an alternating voltage that oscillates with the bias voltage as a reference (center).

  The power supply unit 120 includes a DC power supply 121, an AC power supply 122, and an amplifier 123 that adds the output of the AC power supply 122 to the output of the DC power supply 121, and the output voltage of the amplifier 123 is a discharge needle of the first static elimination unit 81. 831. As a result, the discharge needle 831 is supplied with the output voltage of the DC power supply 121 as a bias voltage, and with the AC voltage output from the AC power supply 122 around the bias voltage. As a result, the discharge needle 831 periodically and positively discharges positive ions and negative ions in response to the supply of an alternating voltage that oscillates with the bias voltage as a reference (center).

  At this time, the DC voltage output from the DC power supply 111 and the DC voltage output from the DC power supply 121 are equal, and the discharge needle 821 and the discharge needle 831 are biased to the same DC voltage. The AC voltage output from the AC power supply 112 and the AC voltage output from the AC power supply 122 have the same amplitude and frequency. However, the phase of the AC voltage output from the AC power source 112 is 180 degrees different from the phase of the AC voltage output from the AC power source 122. As a result, the discharge needle 821 and the discharge needle 831 are supplied with voltages that are mutually inverted with the bias voltage as the center. As a result, ions discharged from the discharge needles 821 and 831 of the first static elimination unit 81 can be efficiently supplied to the sheet S.

  The power supply unit 130 includes a DC power supply 131, an AC power supply 132, and an amplifier 133 that adds the output of the AC power supply 132 to the output of the DC power supply 131, and the output voltage of the amplifier 133 is a discharge needle of the second static elimination unit 85. 861. As a result, the output voltage of the DC power supply 131 is applied to the discharge needle 861 as a bias voltage, and the AC voltage output from the AC power supply 132 is applied around the bias voltage. As a result, the discharge needle 861 periodically and periodically discharges positive ions and negative ions in response to the supply of an alternating voltage that oscillates with the bias voltage as a reference (center). In this example, the amplitude of the AC voltage output from the AC power source 132 is set to be greater than or equal to one and less than twice the amplitude of the AC voltage output from the AC power source 112 or the AC power source 122.

  Furthermore, the printer control unit 100 includes a feedback circuit 140. The feedback circuit 140 outputs the output voltages of the DC power supplies 111 and 121 of the power supply units 110 and 120 based on the detection value of the potential sensor S30, in other words, the discharge needle 821. , 831 is feedback-controlled. Specifically, the output voltages of the DC power supplies 111 and 121 are feedback-controlled so that the voltage detected by the potential sensor S30 approaches the ground potential. Thereby, the ion balance of the 1st static elimination part 81 is adjusted.

  FIG. 6 is a diagram schematically illustrating a temporal change in voltage generated in the sheet by the first static elimination unit and the second static elimination unit. In the figure, the horizontal axis indicates time t, and the vertical axis indicates voltage V. A curve indicated by a solid line indicates a voltage change that occurs in the sheet S by the first static elimination unit 81, and a curve indicated by a broken line indicates a voltage change that occurs in the sheet S by the second static elimination unit 85. The former voltage change may be obtained by measuring the voltage change in the sheet S in the portion sandwiched between the front surface ionizer 82 and the back surface ionizer 83, or the voltage at the tip of each of the discharge needle 821 and the discharge needle 831. It may be calculated from the change and the intervals d82 and d83. Further, the latter voltage change may be obtained by measuring the voltage change in the sheet S of the portion facing the surface ionizer 86, or may be calculated from the voltage change at the tip of the discharge needle 861 and the interval d86. . As a result of setting the amplitude of the AC voltage output from the AC power source 112, the AC power source, and the AC power source 132 as described above, the amplitude of the AC voltage generated in the sheet S by the first static elimination unit 81 is as follows. The amplitude of the AC voltage generated in the sheet S by the second static elimination unit 85 is larger.

  As described above, in the present embodiment, the sheet S is neutralized by the first neutralization unit 81 on the upstream side in the conveyance direction Ds with respect to the front drive roller 31 that drives the sheet S in the conveyance direction Ds. Therefore, since the sheet S has been neutralized when it passes through the front drive roller 31, sticking of the sheet S to the front drive roller 31 is suppressed. As a result, the process tension Tb of the sheet S can be accurately detected in the process unit 3 on the downstream side in the transport direction Ds from the front drive roller 31, and the process tension Tb of the sheet S can be appropriately controlled. It has become. In particular, the process tension Tb of the sheet S between the front driving roller 31 and the rear driving roller 32 is the tension of the sheet S that receives ink ejection from the recording heads 51 and 52 on the peripheral surface of the rotary drum 30. Therefore, the process tension Tb is more important than the other tensions Ta and Tc from the viewpoint of good image recording. Therefore, it can be said that the present embodiment that can appropriately control the process tension Tb is very suitable.

  In addition, a corona treatment device 7 that performs surface modification processing on the sheet S by applying discharge energy to the sheet S on the upstream side in the transport direction Ds from the first static elimination unit 81 is provided. In the printer 1 having such a corona treatment device 7, the charge amount of the sheet S tends to increase, so that the influence on the tension control due to the charged sheet S sticking to the front drive roller 31 also increases. On the other hand, the sheet S can be appropriately tension controlled by discharging the sheet S by the first discharging unit 81 on the upstream side in the transport direction Ds from the front driving roller 31.

  Further, a second static elimination unit 85 that neutralizes the sheet S between the front drive roller 31 and the uppermost recording head 51 in the transport direction Ds is provided. In this way, the sheet S is neutralized in two stages before reaching the recording head 51, so that the sheet S is completely neutralized, and mist-like ink adheres to the recording head 51 due to the charging of the sheet S. Can be suppressed.

  In addition, the second static elimination unit 85 is provided to face the rotating drum 30. As a result, the sheet S can be neutralized in the vicinity of the recording head 51, and it is possible to effectively suppress the mist-like ink from adhering to the recording head 51 due to the charging of the sheet S.

  In the above embodiment, the surface of the rotary drum 30 is covered with the insulating layer. The reason is as follows. That is, when the surface of the rotating drum 30 has conductivity, the ions generated in the second static eliminating portion 85 face the portion of the surface of the rotating drum 30 that is not hidden by the sheet S, and the ions cannot be firmly applied to the sheet S. There is a fear. On the other hand, in the present embodiment, the surface of the rotary drum 30 is covered with an insulating layer, so that ions generated in the second static elimination unit 85 are firmly applied to the sheet S, and the sheet S is more reliably eliminated. It is possible.

  By the way, in the above, in the conveyance direction Ds of the sheet S, the first static elimination unit 81 arranged on the upstream side and the second static elimination unit 85 arranged on the downstream side are provided. In addition, an AC voltage having a relatively large amplitude is generated in the sheet S by the AC voltage applied to the discharge needles 821 and 831 of the first static elimination unit 81. For this reason, ions tend to be concentrated and applied to the sheet S at the portion facing the discharge needles 821 and 831. As a result, there is a large difference in the amount of ions applied between the portion to which ions are applied densely and the portion to which ions are applied sparsely, and the sheet S discharged by the first charge removal portion 81 has uneven discharge. Prone to occur. On the other hand, in this embodiment, the 2nd static elimination part 85 further neutralizes the sheet | seat S after the static elimination by the 1st static elimination part 81. FIG. In addition, as shown in FIG. 6, the AC voltage applied to the discharge needles 821 and 831 of the first static elimination unit 81 is applied to the discharge needles 861 of the second static elimination unit 85 based on the amplitude of the AC voltage generated in the sheet S. The amplitude of the AC voltage generated in the sheet S by the AC voltage is small. Therefore, as compared with the first charge removal unit 81, the second charge removal unit 85 can uniformly remove the sheet S, and the charge removal unevenness of the sheet S after the charge removal by the first charge removal unit 81 can be reduced. It has become. As a result, it is possible to suppress the mist-like liquid from adhering to the recording head 51.

  At this time, the first static elimination unit 81 includes a plurality of discharge needles 821 provided on the front surface side of the sheet S and a plurality of discharge needles 831 provided on the back surface side of the sheet S. The phase of the AC voltage applied to the discharge needle 821 is different from the phase of the AC voltage applied to the plurality of discharge needles 831 on the back side by 180 degrees. In such a configuration, an AC voltage having a relatively large amplitude is generated in the sheet S due to the AC voltage applied to the discharge needles 821 and 831 of the first static elimination unit 81. Therefore, by providing the second charge removal unit 85 as described above, it is preferable to reduce the charge removal unevenness of the sheet S after the charge removal by the first charge removal unit 81.

  Further, the distances d82 and d83 between the discharge needles 821 and 831 of the first charge removal unit 81 and the sheet S are narrower than the distance d86 between the discharge needles 861 and the sheet S of the second charge removal unit 85. In such a configuration, an AC voltage having a relatively large amplitude is generated in the sheet S due to the AC voltage applied to the discharge needles 821 and 831 of the first static elimination unit 81. Therefore, by providing the second charge removal unit 85 as described above, it is preferable to reduce the charge removal unevenness of the sheet S after the charge removal by the first charge removal unit 81.

  Further, the pitches P82 and P83 in which the plurality of discharge needles 821 and 831 are arranged in the first static elimination unit 81 are different from the pitch P86 in which the plurality of discharge needles 861 are arranged in the second static elimination unit 85. As described above, the pitches P82, P83, and P86 at which the discharge needles 821, 831, and 861 are arranged are different between the first static elimination unit 81 and the second static elimination unit 85, so that the sheet after static elimination by the first static elimination unit 81 is performed. The second charge removal unit 85 can effectively mitigate the charge removal unevenness of S.

  Further, DC power sources 111 and 121 that adjust the ion balance of the first static elimination unit 81 and a potential sensor S30 that detects the potential of the sheet S supported by the rotary drum 30 are provided. With such a configuration, the ion balance of the first static elimination unit 81 can be adjusted while confirming the detection result of the potential of the sheet S supported by the rotary drum 30. Therefore, it is possible to optimize the ion balance. As a result, it is possible to suppress the mist-like liquid from adhering to the recording head 51.

  In particular, a feedback circuit 140 is provided that controls the ion balance of the first charge removal unit 81 by causing the DC power supplies 111 and 121 to adjust the ion balance of the first charge removal unit 81 based on the detection result of the potential sensor S30. In such a configuration, the ion balance can be automatically optimized by the feedback circuit 140.

  As described above, in the above embodiment, the printer 1 corresponds to an example of the “printing apparatus” of the present invention, the front drive roller 31 corresponds to an example of the “drive roller” of the present invention, and the rotary drum 30 corresponds to the present invention. The recording heads 51 and 52 correspond to an example of the “ejection head” of the present invention, and the printer control unit 100, the tension sensor S34, the rear driving roller 32, and the rear driving motor M32 cooperate. The first neutralization unit 81 corresponds to an example of the “first neutralization unit” of the present invention, and the sheet S is an example of the “recording medium” of the present invention. The transport direction Ds corresponds to an example of the “predetermined direction” in the present invention, and the process tension Tb corresponds to an example of the “tension” in the present invention. The corona treatment device 7 corresponds to an example of the “discharger” of the present invention, the second charge removal unit 85 corresponds to an example of the “second charge removal unit” of the present invention, and the discharge needle 821 and the discharge needle 831 The discharge electrode 861 corresponds to an example of the “electrode” of the “second charge removal unit” of the present invention, and the interval d82 and the interval d83 correspond to the example of the “electrode” of the “first charge removal unit” of the invention. The distance d86 corresponds to an example of the “interval between the electrode of the first static elimination unit and the recording medium”, and the interval d86 corresponds to an example of the “interval between the electrode of the second static elimination unit and the recording medium” of the present invention. P83 corresponds to an example of the “pitch in which a plurality of electrodes are arranged in the first static elimination section” of the present invention, and the pitch P86 is an example of “a pitch in which the plurality of electrodes are arranged in the second static elimination section” of the present invention. The DC power supply 111 and the DC power supply 121 correspond to an example of the “adjustment unit” of the present invention. Potential sensor S30, corresponds to an example of the "potential detection unit" of the present invention, the feedback circuit 140 corresponds to an example of the "balance control portion" in the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described one without departing from the spirit of the present invention. Therefore, it can also be configured as shown in FIG. Here, FIG. 7 is a block diagram showing a configuration for executing a second control example of the sheet charge removal process. Here, the description will focus on the difference from the configuration shown in FIG. 5, and the common components will be denoted by the corresponding reference numerals, and the description thereof will be omitted as appropriate. However, it goes without saying that the same effect can be achieved by providing the same configuration as described above.

  In the second control example shown in FIG. 7, the printer control unit 100 includes a display control circuit 150, and the display control circuit 150 displays the potential detected by the potential sensor S <b> 30 on the display 91 of the UI 9. Therefore, the user can confirm the potential of the sheet S on the rotary drum 30 by the display 91. The UI 9 is provided with a volume knob 92 that adjusts the output potential of the DC power supply 111 and a volume knob 93 that adjusts the output potential of the DC power supply 121. Therefore, the user can adjust the bias voltage supplied to the discharge needles 821 and 831 by operating the volume knobs 92 and 93 while confirming the potential of the sheet S on the rotary drum 30 by the display 91.

  In this manner, the display 91 (display unit) indicating the detection result of the potential sensor S30 and the volume knobs 92 and 93 (balance control) for causing the DC power sources 111 and 121 to adjust the ion balance of the first static elimination unit 81 in accordance with the input operation. Part). As a result, the user can perform an input operation on the volume knobs 92 and 93 while confirming the detection result of the potential sensor S30 displayed on the display 91 so as to optimize the ion balance.

  Further, the specific configuration of the first static elimination unit 81 may be changed as appropriate. For example, one of the front surface ionizer 82 and the rear surface ionizer 83 may be replaced with a grounded conductor (metal) flat plate, or may be eliminated. In addition, the first ionizer 81 can be configured with a single ionizer by omitting one of the front surface ionizer 82 and the back surface ionizer 83. The pitches P82 and P83 of the discharge needles 821 and 831 and the distances d82 and d83 from the sheet S can be appropriately changed. Furthermore, the arrangement of the first static elimination unit 81 may be changed. For example, the first static elimination unit 81 is arranged between the support roller 71 and the driven roller 21 or downstream of the front drive roller 31 in the transport direction Ds. Also good.

  In addition, the specific configuration of the second static elimination unit 85 may be changed as appropriate. Therefore, the pitch P86 of the discharge needle 861 of the surface ionizer 86 and the distance d86 between the sheet S and the sheet S can be appropriately changed. Further, the arrangement of the second static elimination unit 85 may be changed, or the second static elimination unit 85 may be omitted.

  In the example of FIG. 5, feedback control is performed collectively for the DC power supplies 111 and 121. However, the DC power sources 111 and 121 may be configured to perform feedback control individually. Moreover, in the example of FIG. 7, the structure which adjusts the output potential of DC power supply 111,121 separately was illustrated. However, you may comprise so that the output potential of DC power supply 111,121 may be adjusted collectively. Furthermore, it is not essential to provide the potential sensor S30 or to variably configure the output potential of the DC power supplies 111 and 121.

  In the above embodiment, the sheet S is supported by the cylindrical rotating drum 30. However, the shape of the member that supports the sheet S is not limited to this. For example, the sheet S may be supported by a flat surface.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 31 ... Front drive roller, 30 ... Rotating drum, S30 ... Potential sensor, 51, 52 ... Recording head, S34 ... Tension sensor, 32 ... Rear drive roller, M32 ... Rear drive motor, 7 ... Corona treatment device, 81 ... first static elimination unit, 85 ... second static elimination unit, 821, 831, 861 ... discharge needle, d82, d83, d86 ... interval, P82, P83, P86 ... pitch, S ... sheet, Ds ... conveying direction, Tb ... Process tension, 91 ... Display, 92, 93 ... Volume knob, 100 ... Printer control section, 110 ... Power supply section, 111 ... DC power supply, 112 ... AC power supply, 113 ... Amplifier, 120 ... Power supply section, 121 ... DC power supply, 122 ... AC power supply, 123 ... Amplifier, 130 ... Power supply unit, 131 ... DC power supply, 132 ... AC power supply, 133 ... Amplifier, 140 ... Fed back circuit

Claims (13)

A driving roller for driving the recording medium in a predetermined direction by rotating;
A support member for supporting the recording medium on the downstream side in the predetermined direction from the drive roller;
An ejection head for ejecting liquid onto the recording medium provided opposite to the support member and supported by the support member;
A tension control unit that adjusts the tension of the recording medium supported by the support member by controlling the tension of the recording medium based on the detection result of the tension of the recording medium downstream of the drive roller in the predetermined direction. When,
A printing apparatus comprising: a first static elimination unit that neutralizes the recording medium upstream of the drive roller in the predetermined direction.   The printing apparatus according to claim 1, further comprising: a discharger that performs a surface modification process on the recording medium by applying discharge energy to the recording medium upstream of the first static elimination unit in the predetermined direction.   The printing apparatus according to claim 1, further comprising a second charge removal unit that removes charge from the recording medium between the drive roller and the ejection head.   The printing apparatus according to claim 3, wherein the second static elimination unit is provided to face the support member.   The printing apparatus according to claim 4, wherein a surface of the support member is covered with an insulating layer. The first static elimination unit and the second static elimination unit neutralize the recording medium by applying ions generated by applying an alternating voltage to a plurality of arranged electrodes to the recording medium,
The amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the second charge eliminating unit is smaller than the amplitude of the AC voltage generated in the recording medium by the AC voltage applied to the electrode of the first charge eliminating unit. The printing apparatus according to claim 4 or 5. The first static elimination unit has a plurality of electrodes provided on one side of the recording medium and a plurality of electrodes provided on the other side of the recording medium,
The printing apparatus according to claim 6, wherein the phase of the alternating voltage applied to the plurality of electrodes on the one surface side is different from the phase of the alternating voltage applied to the plurality of electrodes on the other surface side by 180 degrees.   The printing apparatus according to claim 6 or 7, wherein a distance between the electrode of the first charge eliminating unit and the recording medium is narrower than a distance between the electrode of the second charge eliminating unit and the recording medium.   The printing apparatus according to any one of claims 6 to 8, wherein a pitch at which the plurality of electrodes are arranged in the first static elimination unit and a pitch at which the plurality of electrodes are arranged in the second static elimination unit are different. . An adjustment unit for adjusting the ion balance of the first static elimination unit;
The printing apparatus according to claim 1, further comprising a potential detector that detects a potential of the recording medium supported by the support member.   The printing apparatus according to claim 10, further comprising a balance control unit that controls an ion balance of the first charge removal unit by causing the adjustment unit to adjust an ion balance of the first charge removal unit based on a detection result of the potential detector. . A display unit showing a detection result of the potential detector;
The printing apparatus according to claim 10, further comprising: a balance control unit that causes the adjustment unit to adjust an ion balance of the first charge removal unit according to an input operation. Driving the recording medium in a predetermined direction by the driving roller by rotating the driving roller;
Removing the recording medium from the drive roller by a charge removal unit upstream in the predetermined direction;
Adjusting the tension of the recording medium supported by the support member by controlling the tension of the recording medium based on the result of detecting the tension of the recording medium downstream of the drive roller in the predetermined direction;
And a step of discharging liquid from an ejection head facing the support member onto the recording medium supported by a support member provided downstream of the drive roller in the predetermined direction.

Images